Method of manufacturing an inorganic board

ABSTRACT

A mold used for manufacturing an inorganic board and a method of manufacturing an inorganic board by employing said mold are provided in the present invention. Said mold consists of a mold part made of a fiber reinforced plastic and a metal part attached to the back of said mold part, and because of said metal part, the difference in the coefficient of thermal expansion between said mold and an inorganic board manufactured on said mold is small.

This is a continuation of application Ser. No. 08/402,018, filed Mar.10, 1995, now abandoned which was in turn a division of application Ser.No. 08/265,069, filed Jun. 28, 1994, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a mold and a method of manufacturing aninorganic board by employing said mold. Said inorganic board is used asa building material.

DESCRIPTION OF THE PRIOR ART

At present, the semi-dry method is provided to manufacture the inorganicboard. Said method comprises strewing a cement-reinforcing wood materialmixture onto a mold to form a mat, pressing said mat to pre-harden saidmat, and incubating said pre-hardened mat. Generally, said mold has anembossed surface to give a corresponding embossed design to the surfaceof the resulting inorganic board.

Hitherto, a mold made of a fiber reinforced plastic has been providedfor said semi-dry method. Nevertheless, because of the remarkabledifference in the coefficient of thermal expansion between the inorganicboard and said mold, slippage of the interface between the inorganicboard and said mold is caused and said slippage causes the embosseddesign of said inorganic board to become warped.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a moldhaving a coefficient of thermal expansion substantially equal to aninorganic board manufactured on said mold.

Another object of the present invention is to provide an inorganic boardhaving a clear embossed design, without being warped, manufactured byemploying said mold.

Said object may be attained to provide a mold comprising a mold partmade of a fiber reinforced plastic and a metal part attached to the backof said mold part, and a method of manufacturing an inorganic boardcomprising strewing a cement-reinforcing wood material mixture onto saidmold to form a mat, pressing said mat to pre-harden said mat, andincubating said pre-hardened mat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 to FIG. 4 relate to an embodiment of the mold.

FIG. 1 is a plane view of the flat panel-shaped mold.

FIG. 2 is a partial sectional view along line A—A.

FIG. 3 is a sectional view along line B—B.

FIG. 4 is a diagram of an embodiment of the forming machine.

FIG. 5 is a partial sectional view of an inorganic board.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 to FIG. 3 relate to an embodiment of a mold of the presentinvention. Referring now to the Figures, a mold (1) consists of a moldpart (2) made of a fiber reinforced plastic (FRP) and a metal part (3)attached to the back of said mold part (2).

Said fiber reinforced plastic (FRP) is made of a plastic and a fibermixed in said plastic. Said plastic is such as a hardened unsaturatedpolyester, a hardened mixture of unsaturated polyester and styrene, ahardened diallylphatalate, a hardened urea resin, a hardened melamineresin, a hardened phenol resin, a hardened epoxy resin, and the like.Further, said fiber is such as glass fiber, carbon fiber, ceramic fiber,polyester fiber, polyamide fiber, acryl fiber, polyethylene fiber,polypropylene fiber, acetate fiber, and the like.

Said metal part (3) is made of a metal such as iron, aluminum, copper,and the like or an alloy such as a steel, a stainless steel, brass, andthe like, and the coefficient of linear expansion of said metal or alloyis preferably in the range between 10×10⁻⁶/° C. to 30×10⁻⁶.

It is preferable to use an elastic adhesive to attach said metal part(3) to said mold part (2) since said elastic adhesive is easy to followthe thermal deformations of said mold part (2) and said metal part (3).

Said elastic adhesive is made of a synthetic rubber such as acrylrubber, isobutylene-isoprene rubber, silicone rubber, urethane rubber,polysulfide rubber, graft rubber, polybutadiene rubber, polyisoprenerubber, polychloroprene rubber, polyisobutylene rubber, polybutenerubber, isobutene-isoprene rubber, acrylate-butadiene rubber,styrene-butadiene rubber, acrylonitrile-butadiene rubber,pyridine-butadiene rubber, styrene-isoprene rubber,acrylonitrile-chloroprene rubber, styrene-chloroprene rubber and thelike, natural rubber, and/or an elastomer such asstyrene-butadiene-styrene (SBS) copolymer, styrene-isoprene-styrene(SIS) copolymer, styrene-etylene-butylene-styrene (SEBS) copolymer,fluoroestomer and the like.

Said mold (1) has an embossed surface (4) and further longitudinal andhorizontal guide ribs (5) are formed on said surface (4). Instead ofsaid guide ribs (5), guide grooves may be formed on said surface (4).

To manufacture an inorganic board by employing the semi-dry method, acement-reinforcing wood material mixture is strewed on said mold (1) inthe first process (Forming process). Said mixture substantially consistsof a cement, a reinforcing wood material and an aggregate. Said cementis such as Portland cement, blast furnace cement, fly ash cement, silicacement, alumina cement, and the like. Further, said reinforcing woodmaterial is such as wood powder, wood flake, wood pulp, wood fiber,bundled wood fiber, bamboo fiber, hemp fiber, palm fiber, bagasse, ricestraw, wheat straw chaff, and the like. A bulky bundled wood fiber beingbranched and/or curved and/or bent is a preferable reinforcing woodmaterial since said reinforcing wood material gives a porous but strongstructure to the resulting inorganic board. Said bulky bundled woodfiber is disclosed in U.S. Pat. No. 5,188,889. A wood flake is anotherpreferable reinforcing wood material. Said wood flake is made by slicinga wood chip and a preferable wood flake has a width in the range between0.5 to 4 mm, a length in the range between 1 to 30 mm and an aspectratio in the range between 5 to 60. Said reinforcing wood material isgenerally mixed in said cement-reinforcing wood material mixture in theamount of 10 to 35% by weight as a dried fiber to the total solidincluded in said mixture.

Said aggregate is such as a silica sand, a silica powder, a silica fume,a silas balloon, a pearlite, an expansive shale, an expansive clay,burned diatomaceous earth, fly ash, blast furnace slag, gypsum powder,sludge ash, coal cinders, and the like. Said aggregate is generallymixed in said cement-reinforcing wood material mixture in the amount of5 to 15% by weight to the total solid included in said mixture.

Further, if desirable, a hardening promoter such as magnesium chloride,magnesium sulfate, calcium chloride, calcium sulfate, sodium aluminate,potassium aluminate, aluminum sulfate, water glass, and the like, awaterproof agent or water-repellent agent such as wax, paraffin,silicone, a surface active agent, and the like, plastic material such asexpandable polystyrene beads, expandable polyethylene beads, expandablepolypropylene beads, expanded polystyrene beads, expanded polyethylenebeads, expanded polypropylene beads, polystyrene foam, polyethylenefoam, polypropylene foam, and the like, is added.

In the forming process, said mixture is prepared in a mixing machine andwhen said mixture is prepared, the water content of said mixture isadjusted to about 40 to 50% by weight and preferably said mixture isheated at a temperature in the range between about 40 to 70° C. by steamto avoid a deflection of the hardening of said mixture depending on thechanges of the seasons.

To strew said mixture on said mold such as a forming machine (6) showenin FIG. 4 is employed. Referring to FIG. 4, said molds (1) aretransported on a conveyer (7) in the direction showen by arrow C and arelease agent is coated on the surface of said molds (1) respectively byspray guns (8), (8), and then said molds (1) are guided into saidforming machine (6).

Said forming machine (6) comprises a forming chamber (9), a ventilationchamber (10) which is arranged on the exit side of said forming chamber(9) and a ventilator (11) and a heater (12) are installed in saidventilation chamber (10), a reverse ventilator (13) which is arranged inthe entrance side of said forming chamber (9) being opposite to saidventilator (11) in said ventilation chamber (10), a hopper (14) arrangedin the ceiling of said forming chamber (9), a conveyer (15) connectingto said hopper (14) to supply said cement-reinforcing wood materialmixture M onto said hopper (14), a sieve (16) arranged above saidconveyer (15) to strew said mixture M onto said conveyer (15), and adistributing panel (17) arranged in front of said ventilation chamber(10).

Said mixture M is strewed onto said conveyer (15) to put said mixture Min said hopper (14) and then said mixture M is strewed from said hopper(14) onto said mold (1) to form a mat (18) in said forming chamber (9).

During the strewing of said mixture M, the air is heated to atemperature in the range between about 30 to 60° C. by said heater (12)and is blown against said mixture M being strewed.

Thus sad mixture M is distributed by said distributing panel (17) showenby arrow D and accumulates on said mold (1) to form a mat (18). Sincesaid mixture M is sorted depending on the particle size of saidreinforcing wood material in said mixture M by the blown air as abovedescribed, the mixture M including the finer reinforcing wood materialis arranged in the lower part of the resulting mat (18) and the mixtureM including the more coarse reinforcing wood material is arranged in theupper part of the resulting mat (18).

As said mixture M is heated by air heated to a temperature in the rangebetween about 30 to 60° C. during strewing this avoids deflection of thehardening of said mixture depending on the changes of the seasons.

Further, said air is blown against said mixture M being strewed fromsaid reverse ventilator (13) in the direction shown by arrow E to guideand to accumulate said mixture M on the dead space of said mold (1) fromsaid ventilator (11).

The resulting mat (18) formed by the above described forming process hasa structure where the lower part of said mat (18) has a high density andthe upper part of said mat (18) has a low density.

In the present invention, a mat having two or more layers in itsstructure may be also formed. In such a case, where a mat having a twolayer structure is formed, in the first forming stage, a mixture M₁including fine reinforcing wood material is strewed on said mold and inthe second forming stage, a mixture M₂ including coarse reinforcing woodmaterial is strewed on the resulting layer of the first forming stage.

Further, in the present invention, it is not always necessary to heatthe air blown against said mixture M being strewed.

The resulting mat (18) is then pressed if desirable with heating topre-harden said mat (18). If desirable, two or more mats (18) may belaminated before said press process. In a case where two mats (18) arelaminated, it is preferable to laminate said mats (18) by contacting theupper side of each mat (18). As above described, the lower part of saidmat (18) has a high density and the upper part of said mat (18) has alow density, and in a case where two mats (18) are laminated bycontacting the upper side of each mat (18), both surface layers of theresulting inorganic board will consist of lower layers of said mats (18)and a core layer of the resulting inorganic board consists of the upperlayers of said mats (18). Accordingly, in this case, an inorganic boardhaving high density surface layers and a low density core layer ismanufactured. Since said inorganic board has high density and rigidsurface layers and a low density and an elastic core layer, a clearembossed design can be formed on the surface of said inorganic board bypressing with said mold (1). In said pressing process, generally, 2.6 to5.1 MPa of pressure is employed.

During said pressing process, said mixture M in said mat (18) ispre-hardened and the resulting pre-hardened mat (18) is then incubated.In the incubation process, said pre-hardened mat (18) may be removedfrom said mold (1) or said pre-hardened mat (18) may be incubated withsaid mold (1).

In said incubation process, generally, a humidity in the range betweenabout 85 to 95%RH, a temperature in the range between about 50 to 80° C., an incubation time in the range between about 8 to 10 hours areemployed and during said incubation process, the pre-hardened mixture Min said mat (18) is almost completely hardened.

After said incubation process, if desirable, the resulting inorganicboard (19) shown in FIG. 5 is removed from said mold (1) and saidinorganic board (19) has an embossed design (20) formed by the embossedsurface (4) of said mold (1) and guide grooves (21) formed by the guideribs (5) on the surface. Then said inorganic board (19) is cut to asuitable size along said guide grooves (21) as shown by the dotted linel in FIG. 5.

EXAMPLE 1

A mold A used in EXAMPLE 1 consists of a mold part (2) made of an FRPand a metal part (3) made of a steel as shown in FIG. 1 to FIG. 3.

As a comparison, a mold B made of an FRP was prepared. The coefficientsof linear expansion of FRP, steel, and the mold A in said example andthe mold B in comparison are shown in Table 1.

TABLE 1 Coefficient of Linear Expansion FRP 55.1 × 10⁻⁶/° C. Steel 11.8× 10⁻⁶ Mold A 23.6 × 10⁻⁶ Mold B 55.1 × 10⁻⁶/° C.

The formulation of the mixture used in EXAMPLE 1 is as follows;

Portland cement 60 parts by weight Wood flake 25 parts by weightMagnesium chloride 1.2 parts by weight Paraffin 1.0 parts by weightWater 40 parts by weight

Using said mixture M and the mold A and the mold B, inorganic boards Aand B were manufactured by the method in the above described embodiment.The coefficient of linear expansion of the resulting inorganic boardsare respectively 25.0×10⁻⁶ and the condition of the embossed design ofeach inorganic board A or B was observed. As a result, the inorganicboard A manufactured by employing the mold A had a clear embossed designsince the difference of the coefficent of linear expansion between theinorganic board A and the mold A is small while the inorganic board Bmanufactured by employing the mold B had a little warped embossed designsince the difference of the coefficient of the linear expansion betweenthe inorganic board B and the mold B is large.

EXAMPLE 2

A mold C used in EXAMPLE 2 consisted of a mold part (2) made of an FRPand a metal part (3) made of aluminium, the coefficients of linearexpansion of said FRP, said aluminium, and said mold C are shown inTable 2.

TABLE 2 Coefficient of Linear Expansion FRP 55.1 × 10⁻⁶ Aluminium 23.1 ×10⁻⁶ Mold C 27.3 × 10⁻⁶/° C.

An inorganic board C was manufactured by employing mold C and in thesame method as EXAMPLE 1. The resulting inorganic board C had a clearembossed design.

EXAMPLE 3

A mold D used in EXAMPLE 3 consisted of a mold part (2) made of an FRPand a metal part (3) made of stainless steel. The coefficient of linearexpansion of said FRP, said stainless steel, and said mold D are shownin Table 3.

TABLE 3 Coefficient of Linear Expansion FRP 55.1 × 10⁻⁶/° C. Stainlesssteel 14.7 × 10⁻⁶/° C. Mold D 24.0 × 10⁻⁶/° C.

An inorganic board D was manufactured by employing mold D and in thesame method as EXAMPLE 1. The resulting inorganic board D had a clearembossed design.

What is claimed is:
 1. A method comprising the steps of providing arigid fiber-reinforced plastic layer having a molding surface, a backsurface, and a coefficient of linear expansion of approximately55.1×10⁻⁶/° C.; and fixing a metal support to said back surface, saidmetal support having a coefficient of linear expansion within the rangeof 10×10⁻⁶/° C. to 30×10⁻⁶/° C., thereby suppressing the linearcoefficient of expansion of said rigid fiber-reinforced plastic layerand producing a mold having a coefficient of linear expansion within therange of 23.6×10⁻⁶/° C. to 27.3×10⁻⁶/° C.
 2. A method in accordance withclaim 1 further comprising employing an adhesive for attaching saidmetal support to the back surface of said fiber-reinforced plasticlayer.
 3. A method in accordance with claim 1 comprising the step ofembossing said molding surface.
 4. A method in accordance with claim 1comprising the step of reinforcing said fiber-reinforced plastic layerwith fiber selected from the group consisting of glass fiber, carbonfiber, ceramic fiber, polyester fiber, polyamide fiber, acrylic fiber,polyolefin fiber and acetate fiber.
 5. A method in accordance with claim1 comprising the step of selecting said plastic making up saidreinforced plastic layer from the group consisting of hardenedunsaturated polyester, hardened admixture of unsaturated polyester andstyrene, hardened diallylphthatlate, a hardened urea resin, hardenedmelamine resin, hardened phenolic resin and hardened epoxy resin.